A new generation of optoelectronic devices such as organic photovoltaics (OPVs) and organic light-emitting transistors (OLETs) are fabricated using organic semiconductors as their active components. To be commercially relevant, these organic semiconductor-based devices should be processable in a cost-effective manner.
Bulk heterojunction (BHJ) solar cells commonly are considered the most promising OPV structures because they can be fabricated using roll-to-roll and large-scale production. BHJ solar cells include a photoactive layer disposed between an anode and a cathode, where the photoactive layer is composed of a blend film including a donor material and an acceptor material. State-of-the-art BHJ solar cells use fullerene-based compounds as the acceptor material. Typical fullerenes include C60 or C70 “bucky ball” compounds functionalized with solubilizing side chains such as [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) or [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The most common donor material used in BHJ solar cells is poly(3-hexylthiophene) (P3HT). However, it is well known that P3HT-based cell have limited efficiency due to poor light absorption above 500 nm. Furthermore, P3HT also has poor air stability.
Accordingly, the art desires new materials for OPV devices.